| The pressure arch border is studied in this paper, the influence factors, including the buried depth of tunnel〠geotechnical property and span length are discussed. According this theory, critical depth and computational boundary of rock pressure are nonlinear regression analysised.On the basis of this, Surrounding rock pressure formula is calculated.Strength reduction method is put forward on railway tunnel.Reducing cohesion only and reducing angle of internal friction only are very different. The distinct role of both the timing and degree of the work are taken into account. By theoretical derivation and numerical simulation, the relationship between two variables is explored. As a result, the expression of the safety factor is obtained. But, there is an internal connection between rock deformation parameters and strength parameters, and if one is changed,the other is also transformed.The relationship between the elastic modulus and shear strength, between poisson ratio relations and internal friction angle, between tensile strength and shear strength are summarized.On this basis, eight different reduction program is elaborated.At last, the conclusion that taking account of the deformation parameters and strength parameters coordinatly reduction is corresponded to the minimum safety factor and it is the safest design are reached.Composite lining system is made up with primary support and secondary lining. However, there is a different understanding about their rolesat present. In this paper,by using large-scale general software ANSYS, numerical simulation and theoretical analysis are conducted in order to set a composite lining computing model.The realation of deformation compatibility between initial support and secondary lining is analysised. With circular tunnel as an example, the load distribution coefficient of secondary lining is theoretical derivated and verified by ANSYS.Besides,the influence of supporting thickness and lateral pressure coefficient are discussed. |
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